1. Field of the Invention
The present invention relates to a spindle of a machining center, more particularly one, which is structured in such a way that tool releasing and clamping operations can be actuated by means of a clutch, which is connected to the power source, as well as other parts instead of hydraulic mechanisms, and that the number of coil springs used in the spindle can be reduced.
2. Brief Description of the Prior Art
Referring to FIGS. 14 and 15, a conventional spindle 8 of a machining center includes a spindle seat 81, a spindle housing 82, a hydraulic mechanism 84, a pull rod 85, a power source 87, and a main spindle housing 83 fitted in position with the help of both the spindle seat 81 and the spindle housing 82. Oil passages 841, 842 of the hydraulic mechanism 84 are fitted in internal holes 811 of the spindle seat 81 such that a piston 843 can be actuated by means of the hydraulic mechanism 84, which piston 843 is connected to a ring protrusion 851 of the pull rod 85 at a central hole 844 thereof for making the pull rod 85 move together with it. In addition, a shaft coupling device 86 is connected to an upper end of the spindle seat 81, and an output shaft 871 of the power source 87; the output shaft 871 has a through hole 872, which communicates with a rotary connecting head 88 arranged at other end of the power source 87 such that cooling water can be supplied through the pull rod 85 when the machining center is in operation.
From the above description, it can be understood that the hydraulic mechanism 84 is the only mechanism used for actuating the pull rod 85, and movement of a tool shank housing 89 between a clamping position and a releasing one. And, the hydraulic mechanism is difficult to install, repair, and maintain because the oil passages 841, 842 thereof are hidden deep inside the internal holes 811 of the spindle seat 81. Consequently, the spindle is neither efficient nor convenient to use.
Furthermore, in order to use the hydraulic mechanism, the spindle has to be equipped with additional hydraulic units and controlling devices whose cost is relatively high. And, oil leaking and staining is likely to happen, and cost of maintenance of the spindle will increase. Moreover, the spindle will stop functioning when power failure or breakdown of the hydraulic mechanism happens accidentally. Therefore, there will be many problems if a hydraulic mechanism is used as power source for actuating the pull rod of the spindle of a machining center.
Referring to FIG. 16, in order to provide enough elastic force and proper clamping force, another conventional spindle 9 of a machining center is equipped with several coiled springs 92 around a pull rod 91 thereof. In the spindle, a push rod 93 is pivoted to an upper end of the pull rod 91, and a power source is connected to the other end of the push rod 93 so that power of the power source can be passed on to the pull rod 91 through the push rod 93 to effect up and down movement of the pull rod 91, i.e. to move the pull rod 91 between upper and lower positions, in which positions the pull rod 91 will respectively clamp, and release the tool shank housing. However, because displacement and change of length of each coil springs 92 are too small as compared with the distance of displacement of the pull rod 91, there have to be many coil springs 92 arranged around the pull rod 91 to be nearly half of the length of the pull rod 91 all together. Consequently, there will be more difficulty in assembling the spindle, noise and less balance in rotation of the spindle therefore the above structure is not suitable for machining centers of high-speed type.